Re: Role attributes
On May 27, 2009, at 4:40 PM, Dimitri Ostapenko wrote:
Chris Prather wrote:
On Wed, May 27, 2009 at 4:24 PM, Dmitri Ostapenko > wrote:
Is there a way to tell which attributes come from role? I can't
think of a
good way of doing this besides from changing attributes names in
some way.
Using prefix for example..
tx,
What are you trying to achieve?
-Chris
I'm writing interface module for DB table (Pg) that has close
relationship with another table, but does not inherit from it as
each row in main table can have multiple rows in base table. Class
I'm writing needs to interact with both tables.
In case of pure postgres base tables, classes map to tables
beautifully. Base table has corresponding role and child table has
corresponding class. This clean mapping breaks if underlying tables
don't have inheritance.
So using a role to model lower-level table I need to be able to
tell which attributes come from class and which come from role in
methods for saving and retrieving data.
Maybe base class would be better suited for something like this?
Perhaps. However using a custom meta-attribute would work too, like so
(untested):
package MyCustomAttributeMarker;
use Moose::Role;
package SomeRole;
use Moose::Role;
has foo => ( traits => [ 'MyCustomAttributeMarker' ], ... );
package SomeOtherRole;
use Moose::Role;
has bar => ( traits => [ 'MyCustomAttributeMarker' ], ... );
package SomeClass;
use Moose;
with 'SomeRole', 'SomeOtherRole';
has baz => ( ... );
...
my @attrs_from_roles = grep { $_->does('MyCustomAttributeMarker') }
SomeClass->meta->get_all_attributes;
Moose does not provide this by default because the whole purpose of
roles is that they are composed into the class so you don't need to
actually worry about where they came from.
- Stevan
Re: Role attributes
On Wed, May 27, 2009 at 05:20:03PM -0400, Dimitri Ostapenko wrote: > Ah, that would work! That is if I knew how to use traits :) Guess will > have to figure it out If you keep replies on-list, other people can benefit from this conversation in the future. There's a cookbook recipe for the kind of thing I'm suggesting. http://search.cpan.org/~drolsky/Moose-0.79/lib/Moose/Cookbook/Meta/Recipe3.pod hdp.
Re: Role attributes
On Wed, May 27, 2009 at 05:16:28PM -0400, Dimitri Ostapenko wrote: > # Need to know here which attr comes from where to be able to save into > correct table Yes, I understand the problem. That's why I suggested a role for your attribute class so that you can say e.g. has foo => (is => 'ro', ..etc.., from_table => "tablename"); hdp.
Re: Role attributes
Hans Dieter Pearcey wrote:
On Wed, May 27, 2009 at 04:40:37PM -0400, Dimitri Ostapenko wrote:
So using a role to model lower-level table I need to be able to tell
which attributes come from class and which come from role in methods
for saving and retrieving data.
Maybe you want a trait for your attributes that lets you store a table per
attribute definition, or something?
hdp.
!DSPAM:2337,4a1da61670674007936253!
Let's say we have table 'family' and table 'family_member'. Family has
attributes:
- size
- family name
- kind
family_member has:
- sex
- first_name
- age
For a family of 3 there will be 3 rows in 'family_member' for 1 row in
'family'.
package FamilyMember;
use Moose::Role;
use MY::Types;
has 'id' => (is => 'rw', isa => 'PosInt' );
# serial
has 'sex' => (is => 'ro', isa => 'SexType',required=>1);
has 'first_name' => (is => 'ro', isa => 'Str',required=>1 );
has 'age' => (is => 'ro', isa => 'PosInt', default=> 0 );
has 'family_id' => (is => 'ro', isa => 'PosInt', required=>1 ); #
foreign key
package Family;
use Moose;
use MY::Types;
with qw(MY::Base MY::FamilyMember );
has 'id' => (is => 'rw', isa => 'PosInt' );
has 'size' => (is => 'ro', isa => 'PosInt', required=>1);
has 'family_name' => (is => 'ro', isa => 'Str', required=>1 );#
Unique within a table
has 'kind' => (is => 'ro', isa => 'FamilyKind', default=> 'Traditional' );
sub _table { 'family'};
sub _base_table { 'family_member'};
# Return 3 rows from base table, table
sub get {
my (%arg) = @_;
my $id = $arg{id};
my $family_name;
my ($rows,$where);
croak "'id' or 'family_name' is required" unless ($id || $family_name);
if ( $id ) {
$where = "id='$id'";
} else {
$where = "family_name='$family_name'";
}
my $qry = 'SELECT * FROM '. _table().' a,'. _base_table().' b WHERE
a.id=b.family_id AND '.$where;
my $rows = MY::DB::select (sql => $qry, returns => 'hash');
return $rows
}
sub save {
# Need to know here which attr comes from where to be able to save into
correct table
}
Re: Role attributes
On Wed, May 27, 2009 at 04:40:37PM -0400, Dimitri Ostapenko wrote: > So using a role to model lower-level table I need to be able to tell > which attributes come from class and which come from role in methods > for saving and retrieving data. Maybe you want a trait for your attributes that lets you store a table per attribute definition, or something? hdp.
Re: Role attributes
Chris Prather wrote: On Wed, May 27, 2009 at 4:24 PM, Dmitri Ostapenko wrote: Is there a way to tell which attributes come from role? I can't think of a good way of doing this besides from changing attributes names in some way. Using prefix for example.. tx, What are you trying to achieve? -Chris !DSPAM:2337,4a1da1e770674824671560! I'm writing interface module for DB table (Pg) that has close relationship with another table, but does not inherit from it as each row in main table can have multiple rows in base table. Class I'm writing needs to interact with both tables. In case of pure postgres base tables, classes map to tables beautifully. Base table has corresponding role and child table has corresponding class. This clean mapping breaks if underlying tables don't have inheritance. So using a role to model lower-level table I need to be able to tell which attributes come from class and which come from role in methods for saving and retrieving data. Maybe base class would be better suited for something like this?
Re: Role attributes
On Wed, May 27, 2009 at 4:24 PM, Dmitri Ostapenko wrote: > Is there a way to tell which attributes come from role? I can't think of a > good way of doing this besides from changing attributes names in some way. > Using prefix for example.. > > > tx, What are you trying to achieve? -Chris
Re: Role attributes
On Wed, May 27, 2009 at 04:24:07PM -0400, Dmitri Ostapenko wrote: > Is there a way to tell which attributes come from role? I can't think of > a good way of doing this besides from changing attributes names in some > way. Using prefix for example.. Why do you need to know? I can't think of anything offhand that isn't a bad idea. hdp.
